- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Go back to the OP abd read the last sentence.
The OP came to this forum trying to find out why the 400A breaker tripped. How many man-hours has the OP and the affected company invested in "why did this happen'.
My opinion was that a simple explanation of the 'as-installed' coordination as part of a project file, could help in situations where finger pointing may occur.
FWIW, if the OP short circuit allowed >4kA of fault current, the settings of the breakers was likely immaterial.
For most installations coordination is achievable in the area of Line-Ground arcing faults not Line-Line short circuits, so paying for coordination studies does not make sense, except as an insurance policy.